This invention relates to an improved lift pump control for use in material handling vehicles.
In a materials handling vehicle, such as a turret stockpicker, the platform on which the operator rides, and which also carries the load handling forks, is typically raised by hydraulic means. In prior art vehicles, the operator manipulates a handle which in turn controls a valve supplying fluid from a pump to a hydraulic cylinder that lifts the platform. The pump in such a vehicle is normally operated at a speed that will supply the maximum flow of fluid need to raise the platform at the maximum rate. This means that the pump and the motor driving the pump are operated at maximum capacity at all times, even when a much slower rate of platform movement is desired. As a result, smooth and precise control of the platform's movement is sometimes difficult. Also significant power is wasted at lower speeds resulting in excess heat operation and reduced cycle life.